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81.
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Egashira K. Yoshimura Y. Kanno H. Suzuki Y. 《Journal of Thermal Analysis and Calorimetry》2003,71(2):501-508
The thermal decomposition of the lanthanoid trifluoromethanesulfonate (triflate) complexes {Ln(CF3SO3)3·9H2O; Ln=La-Lu{ was studied by TG and DTA methods. From the endothermic and exothermic data of Ln(CF3 SO3)3·9H2O complexes, pyrolysis behavior of the complexes is classified into three groups: 1) La-Nd salts, 2) Sm-Ho salts, 3) Er-Lu
salts. It has also shown that all the final decomposition products were found to result in the formation of LnF3.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
83.
The structure of monomeric and dimeric molecules of scandium tribromide is studied by the synchronous electron diffraction and mass spectrometric experiment at T = 888(10) K and also by the quantum chemical calculations. The experimental data on the structural parameters of ScBr3 molecule were obtained for the first time; also for the first time the molecular structure of Sc2Br6 dimeric molecule was studied. It is found that the ScBr3 molecule has the C 3v effective configuration with the distance r g (Sc-Br) = 2.430(3) Å and the valence angle ∠g(Br-Sc-Br) = 117.6(5)°. The equilibrium structure of the given molecule is planar with D 3h symmetry. According to a theoretical study by DFT and MP2 methods, Sc2Br6 molecule has the equilibrium structure of D 2h symmetry with four Sc-Br bridge bonds. It was confirmed by the results of the electron diffraction analysis. 相似文献
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A scalable homogeneous metal‐catalyzed protocol for direct amidation of carboxylic acids is presented. The use of 2–10 mol% of the commercially available Zr(Cp)2(OTf)2·THF results in high yields of amides at moderate temperature, using an operationally convenient reaction protocol that circumvents the use of water scavenging techniques. 相似文献
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Ke Shen Xiaohua Liu Dr. Ke Zheng Wei Li Xiaolei Hu Lili Lin Dr. Xiaoming Feng Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(12):3736-3742
A direct catalytic asymmetric aldol‐type reaction of 3‐substituted‐2‐oxindoles with glyoxal derivatives and ethyl trifluoropyruvate, catalyzed by a chiral N,N′‐dioxide–Sc(OTf)3 (Tf=trifluoromethanesulfonyl) complex, has been developed that tolerates a wide range of substrates. The reaction proceeds in good yields and excellent enantioselectivities (up to 93 % yield, 99:1 diastereomeric ratio (dr), and >99 % enantiomeric excess (ee)) under mild conditions, to deliver 3‐(α‐hydroxy‐β‐carbonyl) oxindoles with vicinal quaternary–tertiary or quaternary–quaternary stereocenters. Even with 1 mol % catalyst loading or on scaleup (10 mmol of starting material), maintenance of ee was observed, which showed the potential value of the catalyst system. In studies probing the reaction mechanism, a positive nonlinear effect was observed and ScIII‐based enolate intermediates were detected by using ESIMS. On the basis of the experimental results and previous reports, a possible catalytic cycle was assumed. 相似文献
90.
Ibarra IA Lin X Yang S Blake AJ Walker GS Barnett SA Allan DR Champness NR Hubberstey P Schröder M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(46):13671-13679
Two new three-dimensional Sc(III) metal-organic frameworks {[Sc(3)O(L(1))(3)(H(2)O)(3)]·Cl(0.5)(OH)(0.5)(DMF)(4)(H(2)O)(3)}(∞) (1) (H(2)L(1)=1,4-benzene-dicarboxylic acid) and {[Sc(3)O(L(2))(2)(H(2)O)(3)](OH)(H(2)O)(5)(DMF)}(∞) (2) (H(3)L(2)=1,3,5-tris(4-carboxyphenyl)benzene) have been synthesised and characterised. The structures of both 1 and 2 incorporate the trinuclear trigonal planar [Sc(3)(O)(O(2)CR)(6)] building block featuring three Sc(III) centres joined by a central μ(3)-O(2-) donor. Each Sc(III) centre is further bound by four oxygen donors from four different bridging carboxylate anions, and a molecule of water located trans to the μ(3)-O(2-) donor completes the six coordination at the metal centre. Frameworks 1 and 2 show high thermal stability with retention of crystallinity up to 350 °C. The desolvated materials 1a and 2a, in which the solvent has been removed from the pores but with water or hydroxide remaining coordinated to Sc(III), show BET surface areas based upon N(2) uptake of 634 and 1233 m(2) g(-1), respectively, and pore volumes calculated from the maximum N(2) adsorption of 0.25 cm(3) g(-1) and 0.62 cm(3) g(-1), respectively. At 20 bar and 78 K, the H(2) isotherms for desolvated 1a and 2a confirm 2.48 and 1.99 wt% total H(2) uptake, respectively. The isosteric heats of adsorption were estimated to be 5.25 and 2.59 kJ mol(-1) at zero surface coverage for 1a and 2a, respectively. Treatment of 2 with acetone followed by thermal desolvation in vacuo generated free metal coordination sites in a new material 2b. Framework 2b shows an enhanced BET surface area of 1511 m(2) g(-1) and a pore volume of 0.76 cm(3) g(-1), with improved H(2) uptake capacity and a higher heat of H(2) adsorption. At 20 bar, H(2) capacity increases from 1.99 wt% in 2a to 2.64 wt% for 2b, and the H(2) adsorption enthalpy rises markedly from 2.59 to 6.90 kJ mol(-1). 相似文献